Currently, my computer is dual-booting Linux and Windows 7. A series of unfortunate events has led to me needing to restore Windows using a restore disc.

I want to know if this can be done without formatting my entire hard drive, as I don't want to get rid of my Linux partition. That is, I want to reset Windows - which already has a partition on my hard drive - without affecting any of my other partitions on my drive.

The restore could overwrite the Linux partitions (I don't know)..... just make sure you make a backup of all your important data before running the restore.
– WilfJun 6 '15 at 20:49

The information in this link may help answer your question [help.ubuntu.com/community/BootSectorFix] If you Windows recovery disk was created after you installed Ubuntu, it should not hurt your Ubuntu partition. If done before, there is a good chance you could lose your Ubuntu partition, if it does, in fact recover Windows.
– RCFJun 6 '15 at 21:02

3 Answers
3

Restoring Windows will almost definitely break grub, and likely overwrite your linux partitions. You need to backup everything before the restoration, as you'll most likely be reinstalling Ubuntu after it's finished.

While it is possible to install Windows alongside an existing install (of Windows or Linux), by default it expects to replace anything else. That is more a question for a Windows support forum, not AskUbuntu. I would only recommend attempting if you can gain suitable technical understanding of how to control the Windows installer.
– david6Jun 7 '15 at 2:38

2

You're probably right that it isn't impossible, but for someone who has to ask, it is going to be a lot easier to just reinstall Ubuntu after the Windows restoration. Ubuntu was made with dual booting in mind, Windows was not.
– user417599Jun 7 '15 at 3:40

There should be no problems on default Windows 10 installations (UEFI).

I just had to reset one of my Windows 10 installations due to a Windows update error (which I could fix this way) and none of the Grub installations (one SSD with Ubuntu; one HDD with Windows 10, Ubuntu and Fedora) were touched.